Nuclear winter

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Nuclear winter is a hypothetical global climate condition that is predicted to be a possible outcome of a large-scale nuclear war. It is thought that severely cold weather can be caused by detonating large numbers of nuclear weapons, especially over flammable targets such as cities, where large amounts of smoke and soot would be injected into the Earth's stratosphere.

This layer of particles would significantly reduce the amount of sunlight that reached the surface, and could potentially remain in the stratosphere for weeks or even years (smoke and soot arising from the burning petroleum fuels and plastics would absorb sunlight much more effectively than would smoke from burning wood). The ash would be carried by the midlatitude west-to-east winds, forming a uniform belt of particles encircling the northern hemisphere from 30° to 60° latitude. These thick black clouds could block out much of the sun's light for a period as long as several weeks, causing surface temperatures to drop by as much as 30°C during the occlusion.

The combination of darkness and killing frosts, combined with high doses of radiation from nuclear fallout, would severely damage plant life in the region. The extreme cold, high radiation levels, and the widespread destruction of industrial, medical, and transportation infrastructures along with food supplies and crops would trigger a massive death toll from starvation, exposure, and disease. It was also thought that nitrogen oxides generated by the blasts would degrade the ozone layer, as had been observed in the first thermonuclear blasts. Secondary effects from ozone depletion (and concomitant increases in ultraviolet radiation) would be significant, with impacts on the viability of most human staple agricultural crops as well as disruption of ocean food chains by killing off phytoplankton.

1 History
- 1.1 TTAPS (1983)
- 1.2 WCRP report (1986)
2 Kuwait wells in the Gulf War
3 References
4 See also
5 External links

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History

In 1982 a special issue of the journal Ambio was devoted to the possible environmenal consequences of nuclear war; it included an article by Paul Crutzen and J. Birks on atmospheric effects. They re-assessed and re-affirmed the consequences for the ozone layer noted in the 1975 National Academies of Science report (up to 70% of the ozone layer might be destroyed); and drew attention for the first time to the likely large amounts of smoke that would be released.

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TTAPS (1983)

In 1983 the "TTAPS" study (from the initials of the last names of its authors, R.P. Turco, O.B. Toon, T.P. Ackerman, J.B. Pollack, and Carl Sagan) undertook a systematic study of the atmospheric consequences; partly inspired to write the paper both by the suggestions of one Dr. A.M. Salzberg (who, unlike the TTAPS authors, believed that the initial dust thrown into the air would be primarily responsible for the climate changes) and by cooling effects due to dust storms on Mars. To carry out a calculation of the effect they used a simplified two dimensional model of the Earth's atmosphere that assumed that conditions at a given latitude were constant.

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WCRP report (1986)

In 1984 the WMO commissioned G. S. Golitsyn and N. A. Phillips to review the state of the science. They found that studies generally assumed a scenario that half of the worlds nuclear weapons would be used, about 5-6,000 Mt, destroying approximately 1,000 cities, and creating large quantities of black carbonaceous smoke - 1–2 × 10¹⁴ grams being mostly likely, with a range of 0.2 – 6.4 × 10^{14^{(NAS; TTAPS assumed 2.25 × 10¹⁴). The smoke resulting would be largely opaque to solar radiation but transparent to infra-red, thus cooling by blocking sunshine but not causing warming from enhancing the greenhouse effect. The optical depth of the smoke would be four or more. Forest fires resulting from non-urban targets could enhance these numbers. Dust from near-surface explosions against hardened targets could also contribute; each Mt of explosion could release up to 5 Mt of dust, but most would quickly fall out; high altitude dust is estimated at 0.1-1 Mt per Mt of explosion. The theory of large-scale fires was recognised as a weak point; with data from Hamburg and Hiroshima cited as examples. Burning of crude oil could also contribute substantially.}}

The 1-D radiative-convective models used in these studies produced a range of results, with coolings of 15-42 °C between 14 and 35 days after the war, with a "baseline" of about 20 °C. Somewhat more sophisticated calculations using 3-D GCMs (Alexandrov and Stenchikov (1983); Covey, Schneider and Thompson (1984); which would be considered primitive by todays standards) produced similar results: temperature drops of between 20 and 40 °C, though with regional variations.

All calculations show large heating (up to 80 °C) at the top of the smoke layer at about 10 km; this implies a substantial modification of the circulation there and the possibility of advection of the cloud into low latitudes and the southern hemisphere.

The report made no attempt to compare the likely human impacts of the post-war cooling to the direct deaths from explosions.

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Kuwait wells in the Gulf War

The burning of 526 Kuwaiti oil wells during the Persian Gulf War [1] showed the effects of vast emissions of particulate matter into the atmosphere in a geographically limited area; underneath the smoke plume constrained model calculations indicate that the day time temperature dropped by ~10°C within ~200km of the source[2].

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References

Paul J. Crutzen and John W. Birks, "The Atmosphere After a Nuclear War: Twilight at Noon", Ambio, Vol 11, No 2-3, p 114, 1982.
Golitsyn, GS and Phillips, NA. WCRP, Possible climatic consequences of a major nuclear war, WCP-113, WMO/TD #99, 1986.
R.P. Turco, O.B. Toon, T.P. Ackerman, J.B. Pollack, Carl Sagan, "Nuclear Winter: Global Consequences of Multiple Nuclear Explosions", Science, V. 222, No; 4630, December 23, 1983.

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